The statements in this section merely provide background information related to the present disclosure and may or may not constitute prior art.
Long haul trailers of semi-tractors and trailers may readily log over one hundred thousand miles a year. After the tires, the most significant wear item is the interface between the rotating tires and wheels and the stationary axles. This interface includes pairs of roller bearings which support each tire and wheel assembly on each axle.
Although well designed, the failure of the bearings and damage to the terminal portion of the axle, the spindle, is essentially a matter of time. That said, such failures are seldom predictable and it thus has not been found reasonable or economically practical to undertake preventative maintenance which typically includes replacement of these components. The result of the foregoing is that failure of these truck axle components will generally occur without warning and at some distance from a truck terminal or qualified repair facility.
I have therefore developed several on-site axle repair machines, components and procedures that render the repair of such truck axle failures at the failure site rapid, efficient, safe and far less expensive than towing the truck or trailer to a repair facility and replacing the entire axle. For example, my U.S. Pat. No. 6,024,418 discloses a repair method utilizing a long spindle having both inner and outer bearing surfaces and a sleeve or liner. After the damaged end of the axle has been removed, the spindle and liner are installed in the axle and welded at several locations away from regions of significant stress.
Whether completing the repair process described directly above or simply re-assembling a wheel hub and bearings after inspection and lubrication, one of the final steps is the re-installation of a washer and nut to retain the wheel hub and bearings on the threaded spindle. In one arrangement, the nut is a pair of thin nuts. A first or inner nut is tightened down to a specified torque to provide a preload on the bearings and then a second nut is rotated against the first nut to lock it in place.
This arrangement is not ideal for two reasons. First of all, although the first nut can be accurately torqued down to provide the proper bearing preload, when the second (lock) nut is tightened against it, the preload will generally increase to an unknown value. This is because the first nut, as it is tightened or torqued down, is forced away from the bearings and toward the inside faces of the threads on the spindle. However, when the second (lock) nut is tightened against it, it moves slightly inward such that it resides against the outside faces of the threads. This axial translation will increase the bearing preload by some unknown amount. Thus, even if the first nut were initially properly tightened or torqued to apply the proper bearing preload, tightening the second (lock) nut will increase the bearing preload. Second of all, the second (lock) nut which, when tightened, is carrying essentially all of the axial force is thin and can thus distort or damage the small number of spindle threads it is engaging under certain conditions. This, in turn, may make removal of the outer nut difficult or virtually impossible.
Another arrangement utilizes a nut with plural locking features that can be engaged by a pin that is held against rotation by a keyway on the spindle. Again, the nut is torqued down against the wheel and bearings to provide the proper preload. Now, however, since the locking features are spaced about the nut at, for example, 30 degree circumferential intervals, the nut must be rotated (typically back or out) to align a locking feature with the pin. Such rotation changes, and typically reduces, the optimum bearing preload.
From the foregoing, it is apparent that there is a need for improved components and an installation method addressing the problems of properly mounting, preloading bearings and tightening truck axle spindle nuts. The present invention is so directed.